I think with the Belle and the Orion something like this might be do-able.
Memphis Amp:
Ch1+2 = tweets.
Ch2+3 = EF-61CF mids.
Ch5 = EF-8's.
As I'm sure you are already aware, the Baby Belle has the capability to have the LP/HP xovers set to 40 - 6000 Hz with either a 12 or 18 dB slope on Ch 1-4. Only possible drawback = you are limited to a LP 250 Hz max on the 5th channel. While this would be good for pronouncing things like kick drum skin tone (up to around 170-200 Hz) and the lower spectrum of bass guitars (can be as low at 17 Hz, but generally the lowest tuning is 41 Hz), it's not going to allow for much else. I'm a midbass freak and a metal head, so this would actually be music to my ears!
Orion:
Use for sub(s)